Look on my works, ye Mighty, and despair!

Buzzword bingo. If you want to set up an ECS Service (on Fargate), fronted by an ALB (and an API Gateway, and a WAF, and CloudFront – to tick all the boxes), there’s an ansible task for you.

Assuming you already have a task definition, creating a service is pretty straightforward:

- name: Create service
  ecs_service:
    name: ...
    cluster: ...
    task_definition: ...
    network_configuration:
      assign_public_ip: no
      security_groups: ...
      subnets: [...]
    launch_type: FARGATE
    desired_count: ...
    load_balancers: ...

The important bit is the `load_balancers` section. The ansible docs aren’t very informative on this point:

But that just means you need to switch to the AWS docs. You need a list, containing a dict per LB:

    load_balancers:
      -
        targetGroupArn: arn:aws:elasticloadbalancing:region:accountId:targetgroup/serviceName/id
        containerName: ...
        containerPort: 8080

With the arn of the target group that the tasks should be added to/removed from, the name of the container (in case your task definition contains more than one), and the port that traffic should be forwarded to.